This invention relates to materials suitable for the formation of images by exposure to light or other forms of radiation. More particularly, it relates to a positive image-forming material which has high sensitivity and high resolution and is easy to handle.
Among the image-forming materials are positive image-forming materials of which the portion exposed to light or other forms of radiation such as electron beams, X-rays, gamma rays, and alpha rays undergoes a photochemical reaction or degradation reaction and thereby becomes soluble in a liquid developer. These positive image-forming materials are suitable for the formation of fine patterns and for information recording. A number of positive image-forming materials such as quinone diazides, polymethacrylic acid esters, and poly-1-butene sulfone are well known in the prior art, but all of them are low in sensitivity and have small .gamma.-values as calculated from their photosensitivity characteristic curves. Their low sensitivity requires large exposure doses of light or radiation and/or long exposure times and thus cause practical inconvenience. Moreover, their small .gamma.-values causes the incident light or radiation to be reflected or back-scattered from the substrate, making difficult the formation of fine images. Especially in the case of information recording, these positive image-forming materials fail to achieve high resolution and thus lead to a reduction in information storage density.
Many attempts have been made to improve the sensitivity of these conventional positive image-forming materials and enhance the resolution thereof. For example, the use of polymethacrylic acid esters having a molecular weight of 1,000,000 or more has been proposed, but this cannot be regarded as practicable because such polymers are very difficult to synthesize. Thus, these attempts have so far produced no satisfactory results.
Furthermore, these conventional positive image-forming materials have the additional disadvantage that their adhesion to glass substrates, metal substrates, and synthetic resin films is poor. For this reason, the photosensitive layer formed on a substrate often produces pinholes and/or undergoes delamination during its development. This disadvantage can be partially overcome by improving the process conditions, for example, by pretreatment of the substrate with an organosilicone compound or by selection of proper prebaking temperature and time as well as appropriate developing conditions. However, no perfect resolution has been found.